This invention relates to a pipetting device for drawing and dispensing small liquid volumes from approximately 1-1000 nanoliters.
Handheld pipettes are a ubiquitous tool; they are found across industry and academia in essentially all wet laboratories, and are essential to accurate laboratory work in the fields of chemistry, biology, and medicine. They are used for manipulating small volumes of fluid, and still make up the largest percentage of the US liquid handling market. Hand held pipettes offer the convenience, flexibility, ease of use, and low cost that more complex liquid handling solutions cannot offer.
Handheld pipettes operate under very simple physical principles. They consist of several main components: an internal piston, a spring loaded plunger, a disposable tip, an adjustable stop, and a fixed stop. The pipette is held in one hand by the user, and a volume is selected by moving the adjustable stop. The user then presses the plunger down to the adjustable stop. This causes the piston to displace a volume, Vp. The pipette is then lowered into the fluid and the plunger is slowly released. As the spring forces the piston to move back to its initial position, the pressure in the tip lowers and a volume, Vp, of fluid is drawn into the tip. The fluid can then be dispensed into another container by depressing the plunger to the second stop.
As previously mentioned, their ease of use and low cost has led to their widespread adoption; however, there are several important limitations of current handheld pipettes. Pipetting volumes smaller than 1000 nanoliters is challenging and typically imprecise (accuracy ˜25%). Volumes smaller than 100 nanoliters is currently inaccessible. Under the current pipette operating principles, in order to achieve such small volumes, extremely small piston diameters must be used, which are in most cases not manufacturable. Because the piston diameter is fixed, the range of volumes a given pipette can dispense is limited by the piston range. As a result, labs will often have to purchase a variety of pipettes to dispense volumes in every range they may need. Pipette volume resolution is determined by the positional resolution of the hard stop and the diameter of the piston. When purchasing a pipette there is often a tradeoff between resolution and range.
Therefore, current pipetting technology is not suitable for manipulating smaller volumes. Reducing the volumes that a pipette can aspirate and dispense will allow labs to conserve resources, lower their costs, and perform more experiments.